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Why the solubility of alcohols in water increase with branching?

Why the solubility of alcohols in water increase with branching?

Grade:12

3 Answers

dolly bhatia
54 Points
6 years ago
Why the solubility of alcohols in water increase with branching?
Branched chain compounds have lower boiling points than corresponding straight chain isomers.
This is due to the fact that branching of the chain makes molecule more compact and thereby decreases surface area. Thus, intermolecular attractive forces which depend on the surface area, also become small in magnitude on account of branching. Consequently, boiling points of branched chain alkenes are less than straight chain isomers.
Tert-butyl alcohol is more soluble in water than other butyl alcohols.
Reason: Alkyl chain in these molecules is hydrophobic. Greater the surface area of this hydrophobic part, less is the solubility.
In case of tert-butyl alcohol, alkyl group is branched and has less surface area, i.e., less hydrophobic and hence more soluble in water. So, it is almost miscible with water.
Alkyl chain in n-butyl alcohol is linear and has more surface area, i.e., more hydrophobic and less soluble.
Extent of solubility of any alcohol in water depends on capability of its molecule to form hydrogen bonds with water. As molecular mass increases, hydrocarbon part (alkyl group) becomes larger which resists formation of hydrogen bonds with water molecules and hence solubility does on decreasing. So, solubility entirely depends on alkyl group which means larger the alkyl group lesser is the solubility.
But, within isomeric alcohols, solubility increases with branching. This is due to the reason that as branching increase, surface area of non-polar hydrocarbon part decreases and solubility increases.
So, (CH3)3COH is more soluble than butanol in water.
 
Kushagra Madhukar
askIITians Faculty 628 Points
2 years ago
Dear student,
Please find the answer to your question below.
 
Extent of solubility of any alcohol in water depends on capability of its molecule to form hydrogen bonds with water. As molecular mass increases, hydrocarbon part (alkyl group) becomes larger which resists formation of hydrogen bonds with water molecules and hence solubility does on decreasing. So, solubility entirely depends on alkyl group which means larger the alkyl group lesser is the solubility.
But, within isomeric alcohols, solubility increases with branching. This is due to the reason that as branching increase, surface area of non-polar hydrocarbon part decreases and solubility increases.
So, for an example (CH3)3COH is more soluble than butanol in water.
 
Hope it helps.
Thanks and regards,
Kushagra
RISHIKA
550 Points
2 years ago
DEAR FRIEND
Extent of solubility of any alcohol in water depends on capability of its molecule to form hydrogen bonds with water. ... But, within isomeric alcohols, solubility increases with branching. This is due to the reason that as branching increase, surface area of non-polar hydrocarbon part decreases and solubility increases.
THANK U

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